Angiogenesis is a fundamental biologic process involved in wound repair, tissue regeneration, tumor growth, atherosclerosis, and inflammation. The morphology of new capillary growth is well understood, but the cellular and biochemical mechanisms controlling neovascularization are not. Many different recombinant and purified growth factors (aFGF, bFGF, TGF-a, TGF-B, PDGF-AB, PDGF-BB, TNF-a, EGF) have been labelled angiogenic due to their ability to elicit in vivo neovascularization or stimulate one or more of the components of angiogenesis (endothelial cell (EC) proliferation, migration, tube formation or protease synthesis) in vitro. Progress in understanding the biochemical identity and molecular biology of these growth factors has surpassed the basic biological understanding of their role in angiogenesis. with the increasing number of putative angiogenesis factors, the exact mechanism by which each factor elicits new capillary formation and the biological relevance of in vitro data becomes increasingly important. We hypothesize that some factors stimulate angiogenesis by acting directly on the endothelial cells, whereas others act by recruiting inflammatory cells which in turn release direct angiogenesis factors. In addition, we hypothesize that no single growth factor can stimulate all of the components of blood vessel formation. Instead, we believe that combinations of two or more factors in the proper sequence are required for neovascularization. To understand the mechanism behind which each growth factor stimulates or participates in the angiogenic response, a series of carefully controlled in vivo and vitro assays using recombinant and/or purified growth factors are proposed. The rabbit corneal assay with inflammation inhibition studies, histology, histochemistry, autoradiography, transmission electron microscopy, and scanning electron microscopy of vascular casts will reveal which factors act on EC directly or indirectly, as well as the pattern and sequence of blood vessel formation. In vitro studies using rabbit and bovine wound derived capillary EC will determine the role of each factor or combinations of factors in stimulating the individual events of angiogenesis (EC protease synthesis, EC migration, EC proliferation, and EC tube formation). The proposed experiments will result in a clarification of the mechanisms by which the studied growth factors stimulate direct or indirect in vivo angiogenesis, and determine whether a combination of specific factors or factor cascade is required to produce the endothelial cell interactions which result in new capillary formation. In addition, the results will delineate which growth factors should be used in further applied basic science studies on angiogenesis and clinical studies on wound repair, tumor growth, atherosclerosis, and other pathologic states with neovascular components.